1. Field of the Invention
The present invention relates to a method for channel estimation in vehicle-to-environment communication (C2X communication), in which a model of the environment influencing vehicle-to-environment communication is generated from parameters of vehicle-to-environment communication. The quality of the model for the environment is ascertained by the convergence of the parameters used in the model.
2. Prior Art
The data to be transmitted is initially modulated digitally in a digital transmission system. This is also referred to as symbol mapping. A continuous-time baseband signal is generated in a pulse shape filter. Before the signal is able to be transmitted via the actual transmission channel, the baseband signal is transformed into a so-called bandpass signal, for example, with the aid of a quadrature modulator.
On the receiver side, the reception signal is transformed back into a baseband signal via a corresponding quadrature modulator, specific interference suppression mechanisms possibly following after this inverse transformation.
The transmission channel is determined by the physical communications properties of the system. However, it is possible to match the transmitting signal optimally to the properties of the channel using a suitable choice of transmission and modulation methods, which are influenced by the environment of the transmitter and the receiver. On the receiver side, so-called channel estimation is then frequently carried out in order to be able to compensate for distortion occurring via the transmission channel. For this purpose, reference signals are often inserted into the data stream at the transmitter, via which the receiver receives information about the channel transfer function. Based on this information, it is then possible to estimate the channel transfer function with the aid of a model. The known channel estimation methods generate a model of the environment, information from the communication itself being used.
A radar system designed as an environment sensor is known from DE 10256620 A1, which has means for both sensing and data transmission, these means being able to be operated simultaneously using different frequency ranges for sensing and data transmission. Although this has the advantage of making it possible to use largely the same hardware for both data transmission and sensing, various measurements are required, each of which must be activated and evaluated separately.
WO 2006/073691 A2 describes a method in which information about the relative distance between the vehicles is obtained by evaluating a communication channel between two vehicles. For this purpose, current transmission power or transmission power calculated in a model and received transmission strength are taken into consideration, the receiver ascertaining the distance from the transmission power and the received transmission strength based on a model of free radio transmission. This necessarily requires communication between the various communications partners. In addition, satellite positioning systems may be used for improving the determination of the relative distance, transmission losses being determined on the transmission channel between vehicles having a satellite positioning system and being correspondingly used on vehicles without a satellite positioning system, in order to improve the distance estimation for vehicles in the same vehicle cluster. Here as well, an alternative sensor system must be used in order to obtain an assessment of the environment.